Semiconductor light emitting device and method for manufacturing same

ABSTRACT

There are provided a semiconductor light emitting device wherein the variation in tone in each device is small and the variation in tone due to deterioration with age is also small, and a method for manufacturing the same. The semiconductor light emitting device includes an active layer for emitting primary light having a first wavelength by current injection, and a light emitting layer excited by the primary light for emitting secondary light having a second wavelength different from said first wavelength, wherein the primary light and the secondary light are mixed to be outputted.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of priority under 35USC §119 toJapanese Patent Applications No. 2000-066736, filed on Mar. 10, 2000 andNo. 2000-396957, filed on Dec. 27, 2000, the entire contents of whichare incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of The Invention

[0003] The present invention relates generally to a semiconductor lightemitting device and a method for manufacturing the same.

[0004] 2. Related Background Art

[0005] In recent years, semiconductor white light emitting devices arewidely noticed as successors to incandescent lamps and fluorescentlamps. Such a semiconductor white light emitting device is characterizedby a simple driving circuit and small electric power consumption.

[0006] As the semiconductor white light emitting devices, there areproposed devices using GaN compound semiconductor light emittingelements (GaN compound semiconductor white light emitting devices) anddevices using ZnSe compound semiconductor light emitting elements (ZnSecompound semiconductor light emitting devices).

[0007] The GaN compound semiconductor white light emitting devices aredescribed in, e.g., Japanese Patent Laid-Open Nos. 10-242513, 10-12916and 11-121806.

[0008] The GaN compound semiconductor white light emitting devicedisclosed in Japanese Patent Laid-Open No. 10-242513 comprises a GaNcompound semiconductor light emitting element for emitting blue light,and a YAG:Ce fluorescent material for absorbing the emitted blue lightto emit yellow light, to achieve white light by mixing the blue lightemission and the yellow light emission. The YAG:Ce fluorescent materialis mixed in a resin to be applied to a portion surrounding thesemiconductor light emitting element.

[0009] The GaN compound semiconductor white light emitting devicedisclosed in Japanese Patent Laid-Open No. 10-12916 comprises a GaNcompound semiconductor light emitting element for emitting ultravioletlight, and three kinds of fluorescent materials for absorbing theemitted ultraviolet light to emit red light, the green light and theblue light, to achieve white light by mixing red light emission, greenlight emission and blue light emission. The fluorescent materials aremixed in a resin to be applied to a portion surrounding thesemiconductor light emitting element.

[0010] The GaN compound semiconductor white light emitting devicedisclosed in Japanese Patent Laid-Open No. 11-121806 comprises threekinds of active layers including an active layer for emitting red light,an active layer for emitting green light and an active layer foremitting blue light, to achieve white light by mixing the red lightemission, the green light emission and the blue light emission. Thethree kinds of active layers are separately provided, and a current isinjected into each of the active layers.

[0011] A ZnSe compound semiconductor light emitting device comprises aZnSe compound semiconductor light emitting element for emitting bluelight, and an emission center, formed on the substrate, for emittingyellow light, to achieve white light by mixing the blue light emissionand the yellow light emission.

[0012] However, as a result of the inventors' experimental manufactureand evaluation, it was found that, in the conventional semiconductorwhite light emitting devices, there are problems in that the tone ofwhite light varies for each device and that the tone deteriorates withage, as follows.

[0013] First, when a fluorescent material is mixed in a resin to beapplied to a portion surrounding a semiconductor element as in thesemiconductor white light emitting device disclosed in Japanese PatentLaid-Open No. 10-242513, it is difficult to maintain the quantity of thefluorescent material for each element at a constant level, so that thequantity of the fluorescent material varies for each device. Forexample, when the quantity of the fluorescent material is large, theintensity of emitted yellow light is high, so that the tone of whitelight is close to yellow. On the other hand, when the quantity of thefluorescent material is small, the intensity of emitted yellow light islow, so that the tone of white light is close to blue. For that reason,the tone of white light varies for each device. In addition, since thefluorescent material is deteriorates more easily than the semiconductorlight emitting element, the tone greatly deteriorates with age. Forexample, when the fluorescent material deteriorates to and the yellowlight emission weakens the tone is close to blue.

[0014] In addition, when three kinds of fluorescent materials are usedas in the semiconductor white light emitting device disclosed inJapanese Patent Laid-Open No. 10-12916, it is difficult to carry out aproper mixing of the fluorescent materials, so that the compoundingratio of the fluorescent materials varies for each device. For example,when the quantity of the blue light emitting fluorescent material islarge, the tone is close to blue. For that reason, the tone of whitelight varies every device. Also, as in the case of the above describeddevices, the variation in tone due to the variation in quantity of thefluorescent materials, and the variation in tone due to thedeterioration of the fluorescent materials are easily caused.

[0015] In addition, in the structure wherein three kinds of activelayers for red light emission, green light emission and blue lightemission are used as in the semiconductor white light emitting devicedisclosed in Japanese Patent Laid-Open No. 11-121806, the light emissionof each layer varies in accordance with the injected current, so that itis difficult to adjust the balance of light emissions of three colors.For example, when the current injected into the blue light emittingactive layer is too large, the tone of white light is close to blue. Forthat reason, the tone of white light varies.

[0016] Moreover, in the structure wherein an emission center is formedon the substrate as in the ZnSe compound semiconductor light emittingdevice, it is difficult to maintain the quantity of the emission centerat a constant level for each wafer, so that the quantity of the emissioncenter varies for each wafer. For example, when the quantity of theemission center is large, the quantity of emitted yellow light is large,so that the tone of white light is close to yellow. On the other hand,when the quantity of the emission center is small, the quantity ofemitted yellow light is small, so that the tone is close to blue. Forthat reason, the tone of white light varies.

[0017] Thus, it was found that, in the conventional semiconductor whitelight emitting devices, there are problems in that the tone of whitelight varies for each device and that the tone deteriorates with age.

[0018] SUMMARY OF THE INVENTION

[0019] It is therefore an object of the present invention to eliminatethe aforementioned problems and to provide a semiconductor lightemitting device wherein the variation in tone is small and thedeterioration of tone is slow.

[0020] In order to accomplish the aforementioned and other objects,according to one aspect of the present invention, there is provided asemiconductor light emitting device comprising: a semiconductor lightemitting element which has an active layer for emitting primary lighthaving a first wavelength by current injection; and at least onesemiconductor laminate which is bonded to said semiconductor lightemitting element and which has a light emitting layer, excited by saidprimary light, for emitting secondary light having a second wavelengthdifferent from said first wavelength, wherein said primary light andsaid secondary light are mixed to be outputted.

[0021] The active layer may be a In_(p)Ga_(q)Al_(1−p−q)N (0≦p≦1, 0≦q≦1,0≦p+q≦1) active layer. And the InpGa_(p)Ga_(q)Al_(1−p−q)N active layerincludes, for example, an active layer having a multi-quantum wellstructure of InGaN and GaN. The light emitting layer may be anIn_(b)Ga_(c)Al_(1−b−c)P (0≦b≦1, 0≦c≦1, 0≦b+c≦1) light emitting layer.

[0022] According to another aspect of the present invention, there isprovided a semiconductor light emitting device comprising: Asemiconductor light emitting device comprises: a GaAs substrate; anIn_(b)Ga_(c)Al_(1−b−c)P (0≦b≦1, 0≦c≦1, 0≦b+c≦1) light emitting layerwhich is formed on said GaAs substrate and which is excited by primarylight having a first wavelength for emitting secondary light having asecond wavelength; a buffer layer formed on said In_(b) Ga_(c)Al_(1−b−c)P light emitting layer; and a Zn_(j)Cd_(i−j)Se (0≦j≦1) activelayer which is formed on said buffer layer and which emits said primarylight having the first wavelength by current injection; wherein saidprimary light and said secondary light are mixed to be outputted.

[0023] The Zn_(j) Cd_(i−j) Se active layer includes, for example, anactive layer having a multi-quantum well structure of ZnCdSe and ZnSe.

[0024] According to another aspect of the present invention, there isprovided a method for manufacturing a semiconductor light emittingdevice, the method comprising: a semiconductor light emitting elementforming step including a step of forming on a first substrate asemiconductor layers, which has an active layer for emitting primarylight having a first wavelength by current injection; a semiconductorlaminate forming step including a step of forming on a second substratea semiconductor layers, which includes a light emitting layer excited bysaid primary light for emitting secondary light having a secondwavelength different from said first wavelength; and a bonding stepincluding a step of integrally bonding said semiconductor light emittingelement to said semiconductor laminate.

[0025] According to another aspect of the present invention, there isprovided a method for manufacturing a semiconductor light emittingdevice, the method comprising the steps of: forming on a GaAs substratean In_(b) Ga_(c)Al_(1−b−c)P (0≦b≦1, 0≦c≦1, 0 ≦b+c≦1) light emittinglayer, which is excited by blue light for emitting yellow light; forminga buffer layer on said In_(b)Ga_(c)Al_(1−b−c)P light emitting layer; andforming on said buffer layer a ZnCe compound active layer, which emitssaid blue light by current injection.

[0026] According to a further aspect of the present invention, there isprovided a semiconductor light emitting device comprising: a substrate;a buffer layer formed on said substrate; a first conductive typeIn_(r)Ga_(s)Al_(1−r−s)N(0≦r≦1, 0≦s≦1, 0 ≦r+s≦1) cladding layer formed onsaid buffer layer, an In_(p)Ga_(q) Al_(1−p−q)N(0≦p≦1, 0≦q≦1, 0≦p+q≦1)active layer formed on said first conductive typeIn_(r)Ga_(s)Al_(1−r−s)N cladding layer and provided with an ionimplantation region into which ions selected from the group consistingof fluorine, oxygen, nitrogen, carbon and sulfur have been injected,regions other than said ion implantation region emitting primary lighthaving a first wavelength, and said ion implantation region emittingsecondary light having a second wavelength different from said firstwavelength; and a second conductive type In_(t)Ga_(s)Al_(1−t−u)N(0≦t ≦1,0≦u≦1, 0≦t+u≦1) cladding layer formed on said active layer.

[0027] According to a still further aspect of the present invention,there is provided a semiconductor light emitting device comprising: asemiconductor light emitting element which has an active layer foremitting primary light having a first wavelength by current injection;reflector for reflecting said primary light emitted from saidsemiconductor light emitting element; and fluorescent material which isapplied on part of said reflector and which is excited by said primarylight for emitting secondary light having a second wavelength differentform said first wavelength.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be understood more fully from thedetailed description given herebelow and from the accompanying drawingsof the preferred embodiments of the invention. However, the drawings arenot intended to imply limitation of the invention to specificembodiments, but are for the purpose of explanation and understandingonly.

[0029] In the drawings:

[0030]FIG. 1 is a schematic sectional view of the first preferredembodiment of a semiconductor light emitting device according to thepresent invention;

[0031]FIG. 2 is a schematic sectional view showing a method formanufacturing the first preferred embodiment of a semiconductor lightemitting device according to the present invention;

[0032]FIG. 3 is a schematic sectional view showing a method formanufacturing the first preferred embodiment of a semiconductor lightemitting device according to the present invention;

[0033]FIG. 4 is a schematic sectional view of the second preferredembodiment of a semiconductor light emitting device according to thepresent invention;

[0034]FIG. 5 is a schematic sectional view of the third preferredembodiment of a semiconductor light emitting device according to thepresent invention;

[0035]FIG. 6 is a schematic sectional view showing a method formanufacturing the third preferred embodiment of a semiconductor lightemitting device according to the present invention;

[0036]FIG. 7 is a schematic sectional view of the fourth preferredembodiment of a semiconductor light emitting device according to thepresent invention;

[0037]FIG. 8 is a schematic sectional view of the fifth preferredembodiment of a semiconductor light emitting device according to thepresent invention;

[0038]FIG. 9 is a schematic sectional view of the sixth preferredembodiment of a semiconductor light emitting device according to thepresent invention;

[0039]FIG. 10 is a schematic sectional view of the seventh preferredembodiment of a semiconductor light emitting device according to thepresent invention;

[0040]FIG. 11 is a schematic sectional view of the eighth preferredembodiment of a semiconductor light emitting device according to thepresent invention;

[0041]FIG. 12 is a chromaticity diagram for explaining the chromaticityof the eighth preferred embodiment of a semiconductor light emittingdevice according to the present invention, which is an xy chromaticitydiagram defined by International Commission on Illumination (CIE);

[0042]FIG. 13 is a schematic sectional view of the ninth preferredembodiment of a semiconductor light emitting device according to thepresent invention;

[0043]FIG. 14 is a schematic sectional view of the tenth preferredembodiment of a semiconductor light emitting device according to thepresent invention;

[0044]FIG. 15 is a schematic sectional view of the eleventh preferredembodiment of a semiconductor light emitting device according to thepresent invention;

[0045]FIG. 16 is a characteristic diagram showing characteristic of alow-pass filter of the eleventh preferred embodiment of a semiconductorslight emitting device according to the present invention;

[0046]FIG. 17 is a schematic sectional view of the twelfth preferredembodiment of a semiconductor light emitting device according to thepresent invention;

[0047]FIG. 18 is a schematic sectional view of the thirteenth preferredembodiment of a semiconductor light emitting device according to thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] Thirteenth kinds of preferred embodiments of the presentinvention will be described below.

[0049] First, in each of the first through seventh preferredembodiments, there will be described a semiconductor white lightemitting device which comprises a semiconductor light emitting elementfor emitting blue light by current injection, and a semiconductorlaminate for transforming the blue light to emit light of another color,the semiconductor laminate being bonded substantially to the entirelight emitting surface of the semiconductor light emitting element orthe entire opposite surface to the light emitting surface. Among theseembodiments, in each of the first through fifth preferred embodiments, aGaN compound semiconductor light emitting element is used as thesemiconductor light emitting element, and in the each of sixth andseventh preferred embodiments, a ZnSe compound semiconductor lightemitting element is used as the semiconductor light emitting element.

[0050] Then, in each of the eighth through eleventh preferredembodiments, there will be described a semiconductor white lightemitting device which comprises a GaN compound semiconductor lightemitting element for emitting blue light, and a semiconductor laminatehaving a double-hetero structure for transforming the blue light to emityellow light, the semiconductor laminate being bonded to a part of thelight emitting surface of the GaN compound semiconductor light emittingelement or a part of the opposite surface to the light emitting surface.

[0051] Moreover, in each of the twelfth and thirteenth preferredembodiments, there will be described another semiconductor white lightemitting device relevant to the present invention.

[0052] Referring now to the accompanying drawings, the preferredembodiments of a semiconductor light emitting device according to thepresent invention will be described below.

First Preferred Embodiment

[0053]FIG. 1 is a schematic sectional view showing the first preferredembodiment of a semiconductor white light emitting device according tothe present invention. A semiconductor light emitting element 1 foremitting blue light E1 by current injection and a semiconductor laminate2 excited by the blue light E1 for emitting yellow light E2 are bondedto each other at a bonding surface A to constitute a semiconductor whitelight emitting device. As can be seen from FIG. 1, these light beams areemitted from the top side in the figure.

[0054] First, the semiconductor light emitting element 1 will bedescribed. On the top face of a sapphire substrate 104 in the figure,there are sequentially formed a buffer layer 105, an n-type GaN claddinglayer (n-type contact layer) 106, an active layer 107 having a GaN/InGaNmulti-quantum well structure (MQW structure), a p-type AlGaN claddinglayer 108 and a p-type GaN contact layer 109. Furthermore, the “n-typeGaN cladding layer 106” will sometimes be referred to as the “n-typecladding layer 106” herein. The same applies to the other layers.

[0055] A part of the semiconductor light emitting element 1 is etched toexpose the n-type cladding layer 106 to form an n-side electrode 111contacting the n-type cladding layer 106. On the top of the p-typecontact layer 109, a p-side transparent electrode 110 a is formed. Thep-side transparent electrode 110 a is made of a metal thin film or aconductive oxide film, and is capable of transmitting blue light E1emitted from the active layer 107 and yellow light E2 emitted from alight emitting layer 102. Thus the transparent electrode is used, theemission luminance of the device of FIG. 1 increases since the lightemitting surface is arranged on the p-type contact layer 109. On the topof the p-side transparent electrode 110 a, a p-side electrode 110 isformed. A current is injected from the p-side electrode 110 and then-side electrode 111 to emit blue light E1 from the active layer 107.

[0056] The semiconductor laminate 2 will be described below. Thesemiconductor laminate 2 has a structure wherein the light emittinglayer 102 of an InAlP/InGaAlP multilayer film is located between a GaAssubstrate 101 and an InAlP cladding layer (contact layer) 103. The GaAssubstrate 101 has a lattice constant close to that of the light emittinglayer 102 of an InAlP/InGaAlP multilayer film. Therefore, the GaAssubstrate is used for carrying out the crystal growth, the crystallinecharacteristic of the light emitting layer 102 is improved to enhancethe luminous efficiency. The GaAs substrate 101 is non-transparent withrespect to yellow light E2 emitted from the light emitting layer 102 andblue light E1 emitted from the active layer 107. However, since the GaAssubstrate 101 is arranged on the opposite side to the light emittingsurface in the device of FIG. 1, the emission luminance is high even ifthe GaAs substrate 101 exists. For that reason, in the device of FIG. 1,the GaAs substrate is not removed, so that the manufacturing process issimplified. Since the GaAs substrate 101 also has a smaller band gapthan the light emitting layer 102, the GaAs substrate 102 does not serveas the cladding layer of the light emitting layer 102. Therefore, in thesemiconductor laminate 2 of FIG. 1, the light emitting layer 102 is madeof the InAlP/InGaAlP multilayer film, so that electrons and holesgenerated by blue light E1 emitted from the semiconductor light emittingelement 1 can be confined in the light emitting layer 102. Thus thelight emitting layer 102 has the multilayer structure, the luminousefficiency of the emitted yellow light E2 is enhanced, so that theemission luminance of the emitted yellow light E2 increases. In FIG.1the top face of the InAlP cladding layer 103 of the semiconductorlaminate 2 thus constructed is bonded to the bottom face of the sapphiresubstrate 104 of the semiconductor light emitting element 1.

[0057] In the semiconductor light emitting element 1 and semiconductorlaminate 2 described above, blue light E1 having a wavelength of 485 nmis emitted from the active layer 107 of the semiconductor light emittingelement 1 by current injection, a part of the blue light E1 emitteddownward in the figure is incident on the semiconductor laminate 2, andthe incident blue light E1 excites the light emitting layer 102 of thesemiconductor laminate 2 to cause it to emit yellow light E2 having awavelength of 590 nm. Thus, the blue light E1 emitted from the activelayer 107 and the yellow light E2 emitted from the light emitting layer102 can realize white light emission.

[0058] In the semiconductor white light emitting device of FIG. 1, thecolor temperature of white light was about 8000 K, and the luminousintensity during the injection of a current of 20 mA is 2 cd in apackage having a radiation angle of 10 degrees. The color temperature ofwhite light can be controlled by adjusting the emission wavelengths andemission intensities of the semiconductor light emitting element 1 andsemiconductor laminate 2. In the element structure of FIG. 1, thetransparent characteristic of the p-side transparent electrode 110 aalso has an influence on the color temperature and the luminousintensity. That is, since the p-side transparent electrode 110 atransmits light E1 and light E2 having different wavelengths, a requiredcolor temperature can be obtained by adjusting the transmittance foreach light.

[0059] In the semiconductor white light emitting device of FIG. 1described above, it is possible to decrease the variation in tone foreach element. Because the thickness and composition of the semiconductorlaminate 2 hardly vary for each element. That is, by using astandardized mass production process generally used for themanufacturing of semiconductor elements, the semiconductor laminate 2can be manufactured with high repeatability so that the thickness andcomposition hardly vary. Thus the thickness and composition of thesemiconductor laminate 2 are uniform for each element, the ratio of thequantity of the blue light E1 emitted from the semiconductor lightemitting element 1 to that of the yellow light E2 emitted from thesemiconductor laminate 2 does not vary for each device, so that the tonedoes not vary for each device.

[0060] In the semiconductor white light emitting device of FIG. 1, thetone hardly deteriorates with age, because the deterioration with age ofthe yellow light emitting semiconductor laminate 2 is smaller than thatof fluorescent lamps. Since the deterioration with age of thesemiconductor laminate 2 is small, the ratio of the quantity of the bluelight E1 emitted from the semiconductor light emitting element 1 to thatof the yellow light E2 emitted from the semiconductor laminate 2 doesnot vary, so that the tone hardly vary.

[0061] Referring to FIGS. 2 and 3, a method for manufacturing thesemiconductor white light emitting device of FIG. 1 will be describedbelow. As shown in FIG. 2, one of the features of this manufacturingmethod is that a light emitting layer 103 is formed on a GaAs substrate101 suitable for the formation of the light emitting layer 103, andthereafter, this is bonded to a semiconductor blue light emitting device1.

[0062] First, in the manufacturing of the semiconductor laminate 2, aGaAs substrate (a second substrate) 101 is cleaned with an organicsolvent and/or a sulfuric acid containing etchant, and then, the GaAssubstrate 101 is introduced into an MOCVD system. Then, the GaAssubstrate 101 is heated to 730° C., and an appropriate 5-Group materialserving as a P material is supplied to sequentially grow a lightemitting layer 102 of an InAlP/InGaAlP multilayer film and an InAlPcladding layer 103. Further a GaAs cap layer 112 is grown on the surfacethereof. The GaAs cap layer 112 is a protection layer which is finallyremoved. The thickness of these layers are shown in the followingtable 1. TABLE 1 InAlP/InGaAlP Light Emitting Layer 102 30 nm/50 nmInAlP Cladding Layer 103 300 nm or less GaAs Cap Layer 113 100 nm

[0063] Specifically, the light emitting layer 102 has a structurewherein 20 InAlP layers having a thickness of 30 nm and 20In_(0.5)(Ga_(0.) 7Al_(0.3))_(0.5)P layers having a thickness of 50 nmare alternately stacked. The InAlP cladding layer 103 serves as anadhesive layer for bonding the semiconductor laminate 2 to thesemiconductor light emitting element l,also serves and as a protectionlayer for protecting the light emitting layer 102. At the same time ithas the function of confining excitation carriers therein. Since theInGaAlP contact layer absorbs emitted blue light E1, it preferably has athickness of 100 nm or less to reduce light loss due to the absorptionof blue light E1.

[0064] Then, in the manufacturing of the semiconductor light emittingelement 1, as can be seen from FIG. 3, a sapphire substrate (a firstsubstrate) 104 is cleaned with an organic solvent and/or a sulfuric acidcontaining etchant, and then, is introduced into the MOCVD system. Then,after the sapphire substrate 104 is thermally cleaned at 1100° C., abuffer layer 105, an n-type GaN cladding layer 106, a GaN/InGaN activelayer 107 of the MQW structure, a p-type AlGaN cladding layer 108 and ap-type GaN cladding layer 109 are sequentially formed. The growthtemperature and thickness of these layers are shown in Table 2. TABLE 2Buffer Layer 105  500° C. 30 nm n-type GaN Cladding Layer 106 1050° C. 4μm GaN/InGaN Active Layer 107  750° C. 7 nm/3 nm p-type AlGaN CladdingLayer 108 1050° C. 50 nm p-type GaN Contact Layer 109 1050° C. 150 nm

[0065] Specifically, the active layer 107 has a 5QW structure of anIn_(0.35)Ga_(0.65)N layer having a thickness of 3 nm and a GaN layerhaving a thickness of 7 nm.

[0066] Then, the semiconductor light emitting element 1 and thesemiconductor laminate 2 thus manufactured are bonded to each other.Before bonding, the GaAs cap layer 112 formed on the semiconductorlaminate 2 as the protection layer is etched to be removed with asulfuric acid containing etchant. After the GaAs cap layer 112 isremoved, the surface of the InAlP cladding layer 103 is subsequentlycleaned. With respect to the semiconductor light emitting element 1, thebottom side of the sapphire substrate 104 in FIG. 3 is mirror-polishedand simultaneously trimmed to form a flat surface. In order tofacilitate the element isolation which will be carried out later, thetrimming was carried out so that the whole thickness of thesemiconductor light emitting element 1 is about 100 μm.

[0067] Then, the bottom side of the sapphire substrate 104 of thesemiconductor light emitting element 1 in FIG. 3 is aligned with the topside of the InAlP cladding layer 103 of the semiconductor laminate 2 inFIG. 2. Specifically, after the semiconductor light emitting element 1is aligned with the semiconductor laminate 2, they are annealed at 500°C. in an atmosphere of nitrogen for 30 minutes to be bonded to eachother by a dehydrating condensation reaction. In order to improveadhesion, the surfaces to be bonded are preferably as flat as possible.In the planarization of the InAlP cladding layer 103 of thesemiconductor laminate 2, the GaAs substrate 101 inclined in a directionof [011] from the plane (100) is effectively used. In FIG. 2, the GaAssubstrate 101 inclined at 15° is used so that the surface roughness ofthe top side of the InAlP cladding layer 103 in the figure is about 2nm. The surface roughness of the bottom side of the sapphire substrate104 in FIG. 3 is made 20 nm or less by the mirror polishing.

[0068] Then, as can be seen from FIG. 1, a part of the semiconductorlight emitting element 1 is etched from the p-type contact layer 109 tothe n-type cladding layer 106, and then, n-side electrode 111, a p-sidetransparent electrode 110 a and a p-side electrode 110 are formed on theexposed n-type cladding layer 106 and p-type contact layer 109.Moreover, the bottom side of the GaAs substrate 101 is polished ifnecessary.

[0069] The semiconductor white light emitting device of FIG. 1 is thusobtained.

[0070] In the above described method for manufacturing the semiconductorlight emitting device in this preferred embodiment, the light emittinglayer 102 is formed on the top of the GaAs substrate 101 suitable forthe formation of the light emitting layer 102, and, this is bonded tothe semiconductor blue light emitting element 1. Therefore it ispossible to provide a semiconductor white light emitting device whichhas a small number of crystal defects in the light emitting layer 102and which has high reliability.

[0071] In the method for manufacturing the semiconductor light emittingelement in this preferred embodiment, the blue light emittingsemiconductor light emitting element 1 and the yellow light emittingsemiconductor laminate 2 are integrated with each other by bonding tofabricate a single device. Therefore, the device can be used in a spacesmaller than it is used to be in a case where two devices are used, andthe number of electrodes can be reduced. In addition, since the devicecan be regard as a point light source by the integration, it is possibleto provide an element showing a small variation in emitting lights.

Second Preferred Embodiment

[0072] As can be seen from FIG. 4, one of different points of asemiconductor white light emitting device in the second preferredembodiment from the device in the first preferred embodiment (FIG. 1) isthat the substrate 104 side of a semiconductor light emitting element 1serves as a light emitting surface and that a semiconductor laminate 2is bonded to the side of the light emitting surface.

[0073]FIG. 4 is a schematic sectional view showing the second preferredembodiment of a semiconductor white light emitting device according tothe present invention. The same reference numbers are given to elementscorresponding to those in the first preferred embodiment (FIG. 1). As inthe case with the first preferred embodiment (FIG. 1), a semiconductorlight emitting element 1 for emitting blue light E1 from an active layer107 by current injection and a semiconductor laminate 2 excited by theblue light E1 for emitting yellow light E2 from a light emitting layer102 are bonded to each other at a bonding surface A to constitute asemiconductor white light emitting device. As can be seen from FIG. 4,these light beams are emitted from the top side in the figure.

[0074] First, the semiconductor light emitting element 1 will bedescribed. One of different points of the semiconductor light emittingelement 1 from that in the first preferred embodiment (FIG. 1) is thatthe transparent electrode 110 a is not used as a p-side electrode. Inthe semiconductor light emitting element 1 of FIG. 4, a p-side electrode110 of Ni/Au or the like having a high reflectance is formedsubstantially on the entire surface of a p-type contact layer 109. Thus,the blue light E1 emitted downward from the active layer 107 in thefigure can be reflected on the p-side electrode 110 to be effectivelyemitted from the light emitting surface on the top side in the figure.Other principal features are the same as those in the first preferredembodiment.

[0075] The semiconductor laminate 2 will be described below. One ofdifferent points of the semiconductor laminate 2 from that in the firstpreferred embodiment (FIG. 1) is that the GaAs substrate 101 is removedand an SiO₂ protection layer 201 is formed on that surface. This is forpreventing light from being absorbed into the GaAs substrate 101. Thatis, in the device of FIG. 4, the semiconductor laminate 2 is bonded tothe light emitting surface. Accordingly if the GaAs substrate exists,the emitted blue light E1 and yellow light E2 are absorbed into the GaAssubstrate if the GaAs substrate exists. Therefore, the GaAs substrate isremoved to enhance the emission luminance.

[0076] A process for manufacturing the semiconductor light emittingelement 1 and the semiconductor laminate 2 is basically the same as thatin the first preferred embodiment. Specifically, the InAlP/InGaAlPmultilayer film 102 is formed so as to have a structure that 10 InAlPlayers and 10 In_(0.5)(Ga_(0.7)Al_(0.3))_(0.5)P layers are alternatelystacked. The GaAs substrate is removed with a hydrofluoric acidcontaining etchant.

[0077] The semiconductor white light emitting device of FIG. 4 thusobtained was mounted on a package so that the electrodes 110 and 111faced downward, and a current was injected. As a result, the blue lightE1 having a wavelength of 485 nm was emitted from the active layer 107,and the yellow light E2 having a wavelength of 590 nm was emitted fromthe light emitting layer 102 by exciting the blue light E1. These lightbeams passed through the oxide film 201 to be observed as white light.The color temperature of white light was about 8000 K, and the luminousintensity during the injection of a current of 20 mA was 3cd in apackage having a radiation angle of 10 degrees.

[0078] Even if the light emitting surface is arranged on the side of thesubstrate 104 as in this preferred embodiment, it is possible todecrease the variation in tone in each device and the variation in tonedue to deterioration with age, as in the case with the first preferredembodiment.

Third Preferred Embodiment

[0079] As can be seen from FIG. 5, one of different points of asemiconductor white light emitting device in the third preferredembodiment from the device in the second preferred embodiment (FIG. 4)is that two light emitting layers 302 and 304 are formed in asemiconductor laminate 2.

[0080]FIG. 5 is a schematic sectional view showing the third preferredembodiment of a semiconductor white light emitting device according tothe present invention. The same reference numbers are given to elementscorresponding to those in the second preferred embodiment (FIG. 4). Asemiconductor light emitting element 1 for emitting blue light E1 froman active layer 107 by current injection and a semiconductor laminate 2,which is excited by the blue light E1 for emitting green light E2 from afirst light emitting layer 304 and which is excited by the green lightE2 and the blue light E1 for emitting red light E3 from a second lightemitting layer 302, constitute a semiconductor white light emittingdevice. As can be seen from FIG. 5, these light beams are emitted fromthe top side in the figure.

[0081] First, the structure of the semiconductor light emitting element1 is basically the same as that in the second preferred embodiment (FIG.4), so that the detailed description thereof is omitted.

[0082] The semiconductor laminate 2 will be described below. Between thefirst light emitting layer 304 and the second light emitting layer 302,a first InAlP cladding layer 303 is provided. On the bottom face of thefirst light emitting layer 304 in the figure, a second InAlP claddinglayer 305 for bonding the semiconductor laminate 2 to the semiconductorlight emitting element 1 is formed. The top face of the second lightemitting layer 302 in the figure is covered with an oxide film 306 whichis a protection layer.

[0083] When a third InAlP cladding layer (not shown) is provided betweenthe oxide film 306 and the second light emitting layer 302, it ispossible to adjust tone. That is, when the third InAlP cladding layer isprovided, carriers are effectively confined in the second light emittinglayer 302, so that the quantity of red light E3 increases, and the bluelight E1 is absorbed into the third InAlP cladding layer, so that thequantity of blue light E1 decreases.

[0084] As shown in FIG. 5, in the above described semiconductor lightemitting element 1 and semiconductor laminate 2, the side of theprotection layer 306 of the semiconductor laminate 2 serves as a lightemitting surface to obtain white color due to the color mixture of threeemissions E1, E2 and E3. That is, the current is injected into thesemiconductor light emitting element 1 to obtain the blue light E1emitted from the active layer 107 having the MQW structure, and thefirst light emitting layer 304 of the semiconductor laminate 2 isexcited to obtain the green light 2. Moreover, the second light emittinglayer 302 is excited with the emitted blue light E1 and green light E2to obtain the red light E3. By the hybridization of these light beams,white light is obtained.

[0085] Specifically, blue light E1 having a wavelength of 485 nm wasemitted from the MQW layer 107, green light E2 having a wavelength of565 nm was emitted from the first light emitting layer 304, and redlight E3 having a wavelength of 620 nm was emitted from the second lightemitting layer 302, so that white light was observed by the colormixture. The color temperature of white light was about 6500 K. Theluminous intensity during the injection of a current of 20 mA was 2 cdin a package having a radiation angle of 10 degrees.

[0086] Even in the case of the semiconductor white light emitting devicefor obtaining white light by the color mixture of blue light E1, greenlight E2 and red light E3, it is possible to reduce the variation intone in each device and the variation in tone due to deterioration withage, as in the case with the first preferred embodiment.

[0087] In the device of FIG. 5, the blue light E1 is emitted by thecurrent injection, whereas the green light E2 and the red light E3 areemitted by optical pumping. Therefore, the variation in tone in eachdevice due to the lost balance of current injection doe not occur. Forexample, in a case where a current is injected into each of the bluelight emitting active layer, the green light emitting active layer andthe red light emitting active layer to obtain white light, when thequantity of the current injected into the blue light emitting activelayer increases due to the lost balance of current injection, the toneis caused to near to blue. However, in the device of FIG. 5, such avariation in tone in each device does not occur.

[0088] Referring to FIG. 6, a method for manufacturing the semiconductorwhite light emitting device of FIG. 5 will be described below. As shownin FIG. 6, one of the features of this manufacturing method is that afirst light emitting layer 304 and a second light emitting layer 302 areformed on a GaAs substrate 301 suitable for the formation of the lightemitting layers 304 and 302, and thereafter, this is bonded to asemiconductor light emitting device 1.

[0089]FIG. 6 shows the structure of the semiconductor laminate 2 in thesecond preferred embodiment before the bonding. This will bespecifically described in accordance with manufacturing steps.

[0090] First, a GaAs substrate 301 is cleaned with an organic solventand/or a sulfuric acid containing etchant, and then, the substrate isintroduced into an MOCVD system. Then, the substrate is heated to 730°C., and an appropriate 5-Group material serving as a P material issupplied to sequentially crystal-grow a second light emitting layer 302of an InAlP/InGaAlP multilayer film, a first InAlP cladding layer 303, afirst light emitting layer 304 of an InAlP/InGaAlP multilayer film, anda second InAlP cladding layer 305 to further grow a GaAs cap layer 307on the surface thereof to obtain a stacked structure shown in FIG. 6.The GaAs cap layer 307 is a protection layer which is ultimatelyremoved.

[0091] The thickness of these crystalline layers are shown in Table 3.InAlP/InGaAlP Light Emitting Layer 302 30 nm/50 nm InAlP Cladding Layer303 500 nm or less InAlP/InGaAlP Light Emitting Layer 304 30 nm/50 nmInAlP Cladding Layer 305 300 nm or less GaAs Cap Layer 307 100 nm

[0092] Specifically, the second light emitting layer 302 has a structurewherein 20 InAlP layers having a thickness of 30 nm and 20In_(0.5)(Ga_(0.8)A_(0.2))_(0.5)P layers having a thickness of 50 nm arealternately stacked. The first light emitting layer 304 has a structurewherein 20 InAlP layers having a thickness of 30 nm and 20In_(0.5)(Ga_(0.5)Al_(0.4))_(0.5)P layers having a thickness of 50 nm arealternately stacked. The InAlP contact layer 305 serves both as anadhesive layer for bonding the semiconductor laminate 2 to thesemiconductor light emitting element 1 and as a protection layer forprotecting the light emitting layer 304, and at the same time, also havethe function of confining light in the light emitting layer 304.

[0093] Then, the cap layer 307 of the semiconductor laminate 2 thusmanufactured is removed, and the semiconductor laminate 2 is bonded tothe semiconductor light emitting element 1 as in the case with the firstpreferred embodiment. Then, the GaAs substrate 301 is etched to beremoved, and a protection layer 306 is formed on the surface thusetched, so that the device structure of FIG. 5 is obtained.

[0094] In the above described method for manufacturing the semiconductorlight emitting device of FIG. 5, as in the case with the first preferredembodiment, the light emitting layers 302 and 304 are formed on the topof the GaAs substrate 301 suitable for the formation of the lightemitting layers 302 and 304, and thereafter, this is bonded to thesemiconductor blue light emitting element 1, so that it is possible toprovide a semiconductor white light emitting device which has a smallnumber of crystal defects in the light emitting layers 302 and 304 andwhich thus has high reliability.

[0095] In the method for manufacturing the device wherein thesemiconductor laminate 2 is provided on the side of the light emittingsurface, as shown in FIG. 5, it is possible to prevent light from beingabsorbed into the GaAs substrate 301 by etching and removing the GaAssubstrate 301, so that it is possible to enhance the emission luminanceof the device.

[0096] In the method for manufacturing the semiconductor light emittingdevice of FIG. 5, the semiconductor light emitting element 1 foremitting blue light E1 and the semiconductor laminate 2 for emittinggreen light E2 and red light E3 are integrated with each other bybonding to fabricate a single device. Therefore, the device can be usedin a smaller space than that in a case where two or three devices areused, and the number of electrodes can be reduced. In addition, sincethe device can be regarded as a point light source by the integration,it is possible to provide a device having a small variation in emission.

Fourth Preferred Embodiment

[0097] As can be seen from FIG. 7, one of different points of asemiconductor white light emitting device in the fourth preferredembodiment from the device in the first preferred embodiment (FIG. 1) isthat an n-type semiconductor substrate 404 such as an n-type GaN, n-typeSiC, n-type Si substrate is used as the substrate of a semiconductorlight emitting element 1, and that an n-type electrode 111 is formed onthe reverse surface of the substrate 101 n of a semiconductor laminate2. In the device of FIG. 7, a current is injected from the n-sideelectrode 111 into an active layer 107 via an n-type GaAs substrate 101n, a light emitting layer 102 n of an n-type InAlP/InGaAlP multilayerfilm, an n-type InAlP cladding layer 103 n, an n-type semiconductorsubstrate 404, an n-type AlGaN buffer layer 105 n and a GaN contactlayer 106. Other principal structures are the same as those in the firstpreferred embodiment.

[0098] Even in the case of the semiconductor light emitting devicewherein the electrodes are provided on the top and bottom as shown inFIG. 7, it is possible to reduce the variation in tone in each deviceand the variation in tone due to deterioration with age, as in the casewith the first preferred embodiment.

[0099] Even in the case of the device of FIG. 7, it is possible to use amanufacturing method which is substantially the same as that in thefirst preferred embodiment (FIG. 1), and it is possible to obtain adevice having high reliability, as in the case with the first preferredembodiment. Moreover, in the case of the device of FIG. 7, an etchingstep of forming an n-side electrode is not required to carry out, sothat the manufacturing method is simplified.

Fifth Preferred Embodiment

[0100] As can be seen from FIG. 8, one of different points of asemiconductor white light emitting device in the fifth preferredembodiment from the device in the first preferred embodiment (FIG. 1) isthat the non-transparent GaAs substrate 101 of a semiconductor laminate2 is etched to be removed and that another transparent substrate 501 isbonded to a bonding surface A2. Specifically, a GaP substrate or ZnSesubstrate for transmitting yellow light is used as the transparentsubstrate 501. Other principal structures are the same as those in thefirst preferred embodiment. Furthermore, the bonding surface A in thefirst preferred embodiment (FIG. 1) corresponds to the bonding surfaceAl in the fifth preferred embodiment (FIG. 8).

[0101] In the device of FIG. 8, yellow light E2s emitted from anInAlP/InGaAlP light emitting layer 102 can also be emitted from the sideof the newly bonded substrate 501 as shown by a broken line. Therefore,if, for example, when the inner wall surface of a package is formed as arecessed surface to emit the radiation E2s upward, the radiation E2s canbe effectively utilized.

[0102] In the above described first through fifth preferred embodiments,an InAlP layer 103 was used as a cladding layer (also serving as acontact layer) for bonding the light emitting layer 102 of asemiconductor laminate 2 to a semiconductor light emitting element 1. Onthe top of the InAlP cladding layer 103, a cladding layer of anothermaterial may be formed in place of the cladding layer 103. Such acladding layer may be made of, e.g., GaN or GaP. By providing such acladding layer, the light confining effect in a multilayer film 102 canbe enhanced. A GaN cladding layer is particularly preferable since ittransmits blue light, though it is a polycrystalline thin film. Inaccordance with the material of a substrate to be bonded, GaAlAs orInGaAlP may be used.

[0103] Although etching and/or polishing was used as a pre-treatmentbefore bonding, gas etching or thermal cleaning in various amorphousgases may be carried out. Moreover, the annealing atmosphere andtemperature can be suitably changed. When a high annealing temperatureis used, an atmosphere gas may be selected to apply a suitable pressurein order to prevent atoms from being emitted and removed from crystal.

[0104] For bonding, an adhesive may be used. For example, if an adhesiveis used in the device in the fifth preferred embodiment (FIG. 5),setting the refractive index of the adhesive to be at a value betweenthe refractive index of the sapphire substrate 104 and the refractiveindex of the InAlP cladding layer, enables the reduction in quantitiesof blue light E1 and yellow light E2 reflected on the bonding surfaceAl, so that it is possible to enhance the emission luminance of thedevice.

Sixth Preferred Embodiment

[0105]FIG. 9 is a schematic sectional view of the sixth preferredembodiment of a semiconductor white light emitting device according tothe present invention. Unlike the preceding preferred embodimentswherein the semiconductor light emitting device is bonded to thesemiconductor laminate, a light emitting layer 702 and an active layer706 in this preferred embodiment, are formed on an n-type GaAs substrate701 by crystal growth. That is, on the n-type GaAs substrate 701, thereare sequentially stacked an n-type InAlP/InGaAlP light emitting layer702 for emitting yellow light E2 by optical pumping, an n-type ZnSebuffer layer 703, an n-type ZnMgSSe cladding layer 704, an n-type ZnSeoptical guiding layer 705, a ZnSe/ZnCdSe MQW active layer 706 foremitting blue light E1 by current injection, a p-type ZnSe opticalguiding layer 707, a p-type ZngSSe cladding layer 708, and a p-typeZnTe/ZnSe superlattice contact layer 709. On the p-type contact layer709, a p-side transparent electrode 710 a and a p-side electrode 710 areformed, and on the n-type GaAs substrate 701, an n-side electrode 711 isformed.

[0106] For the crystal growth of the device of FIG. 9, the MOCVD methodand the MBE method are combined. That is, the MOCVD method is used forthe crystal growth of the n-type InalP/InGaAlP light emitting layer 702on the n-type GaAs substrate 701, and the MBE method was used for thegrowth of the n-type ZnSe buffer layer 703 to the p-type ZnTe/ZnSesuperlattice contact layer 709 thereon. This is because a goodconductive type control can be achieved by using the MBE methodparticularly for ZnSe compound p-type conductive layers.

[0107] In the semiconductor white light emitting device thus formed,blue light E1 is emitted from the active layer 706 by passing a currentbetween the electrodes 710 and 711. A part of the blue light E1 passesthrough the element to be absorbed into the light emitting layer 702 toexcite yellow light E2. This yellow light E2 is emitted from the topside in the figure. By the hybridization of the blue light E1 and yellowlight E2, white light is obtained.

[0108] In fact, white light was observed by the color mixture of bluelight E1 having a wavelength of 485 nm and yellow light E2 having awavelength of 590 nm. The color temperature of the white light was about8000 K, and the luminous intensity during the injection of a current of20 mA was 2 cd in a package having a radiation angle of 10 degrees.

[0109] Even in the case of the above described semiconductor lightemitting device of FIG. 9 using the ZnSe compound semiconductor lightemitting element 1, it is possible to reduce the variation in tone ineach device and the variation in tone due to deterioration with age, asin the case with the first preferred embodiment.

[0110] A method for manufacturing the device of FIG. 9 will be brieflydescribed below. First, an n-type GaAs substrate 701 is cleaned with anorganic solvent and/or a sulfuric acid containing etchant, and then, thesubstrate is introduced into an MOCVD system. Then, the substrate isheated to 730° C., and an appropriate 5-Group material serving as a Pmaterial is supplied to grow an n-type InAlP/InGaAlP light emittinglayer 702. Then, the substrate is transferred to an MBE system to growthereon an n-type ZnSe buffer layer 703 to a p-type ZnTe/ZnSesuperlattice contact layer 709. Specifically, the n-type InAlP/InGaAlPlight emitting layer 702 was formed so as to have a structure wherein 20InAlP layers and 20 In_(0.5)(Ga_(0.7)Al_(0.3))_(0.5)P layers arealternately stacked.

[0111] As described above, in the semiconductor light emitting device ofFIG. 9, the n-type InAlP/InGaAlP light emitting layer 702 and theZnSe/ZnCdSe MQW active layer 706 are formed on the n-type GaAs substrate701 by crystal growth, so that it is possible to simplify themanufacturing process.

[0112] In addition, since the lattice constant of the ZnSe compoundsemiconductor is close to the lattice constant of the GaAs compoundsemiconductor, even if the above described crystal growth is carriedout, it is possible to provide a semiconductor white light emittingdevice which has a small number of crystal defects and which has highreliability.

Seventh Preferred Embodiment

[0113] As can be seen from FIG. 10, one of different points of asemiconductor white light emitting device in the seventh preferredembodiment from the device in the sixth preferred embodiment (FIG. 9) isthat etching is carried out from the side of a p-type contact layer 709to expose an n-type buffer layer 703 and that an n-side electrode 711 isformed on the n-type buffer layer 703. Other principal constructions arethe same as those in the sixth preferred embodiment.

[0114] Even in the case of the device of FIG. 10, it is possible toobtain white light by color mixture as in the case with the sixthpreferred embodiment, so that it is possible to obtain the sameadvantages as those in the sixth preferred embodiment.

[0115] While the InGaAlP materials semiconductors and the ZnSe compoundsemiconductors have been crystal-grown by the MOCVD method and the MBEmethod, respectively, in the sixth and seventh preferred embodiments,both may be crystal-grown by the MBE method. Also in the case of thematerial system in the sixth and seventh preferred embodiments, twolight emitting layers may be formed on separate element substrates,respectively, to bond and integrate the substrates with each other as inthe case with the first preferred embodiment.

Eighth Preferred Embodiment

[0116] In the following eighth through eleventh preferred embodiments,there will be described a device wherein a semiconductor laminate 2having a double-hetero structure is bonded to a part of a light emittingsurface of a GaN compound semiconductor light emitting element 1 or apart of the opposite surface thereto, as shown in, e.g., FIG. 11.Furthermore, in the following preferred embodiments, the detaileddescription of the manufacturing process is omitted.

[0117]FIG. 11 is a schematic sectional view showing the eighth preferredembodiment of a semiconductor white light emitting device according tothe present invention. The same reference numbers are given to elementscorresponding to those in the first preferred embodiment (FIG. 1). Asemiconductor white light emitting device comprises a semiconductorlight emitting element 1 for emitting blue light E1 by currentinjection, and a semiconductor laminate 2 excited by the blue light E1for emitting yellow light E2. As can be seen from FIG. 12, these lightbeams are emitted from the top side in the figure.

[0118] First, the semiconductor light emitting element 1 will bedescribed. On the bottom face of a sapphire substrate 104 in the figure,there are sequentially formed a buffer layer 105, an n-type GaN claddinglayer 106, an InGaAlN active layer 107 a, a p-type AlGaN cladding layer108 and a p-type GaN contact layer 109. Although the thickness of eachof the layers 104 to 109 is several μm and the thickness of the sapphiresubstrate 104 is hundreds μm, the scale factor thereof is changed inFIG. 11 for the purpose of easier explanation of the stacked layers 104through 109.

[0119] The wavelength of light emitted from the above described InGaAlNactive layer 107 is designed to emit blue light E1 by controlling thecomposition ratio of In and Al of the active layer. The compositionratio of Al may be 0 so that the active layer is made of InGaN. If thisactive layer 107 a has a single-quantum well or multi-quantum wellstructure of a thin film having a thickness of about 1 nm to 10 nm, itis possible to realize high luminance. A current is injected into theactive layer 107 a from an n-side electrode 111, which is formed on then-type cladding layer 106, and from a p-side electrode 110 which isformed on the p-type contact layer 109. The p-side electrode 110 and then-side electrode 111 are preferably made of Ni/Au and Ti/Al,respectively, which are materials having a high reflectance forreflecting blue light emitted from the active layer 107 a. Thus, theblue light E1 emitted from the active layer 107 a downward in the figurecan be reflected on the p-side electrode 110 and the n-side electrode111 to be emitted from the light emitting surface on the top side in thefigure. Furthermore, the portions shown by slant lines in the figure,such as the p-side electrode 110 and the n-side electrode 111, are theportions having the property of reflecting the blue light E1 and theyellow light E2.

[0120] The semiconductor laminate 2 will be described below. Thesemiconductor laminate 2 has a structure wherein an InGaAlP lightemitting layer 102 c is located between a p-type InGaAlP cladding layer102 b and an n-type InGaAlP cladding layer 102 a. The light emittinglayer 102 c is designed to emit the yellow light E2 by controlling thecomposition ratio of 3-Group elements, In, Ga and Al, of InGaAlP. Thethickness of the light emitting layer 102 is preferably in the range offrom 1 nm to 10 nm. That is, when the light emitting layer 102 c has asingle-quantum well or multi-quantum well structure of a thin filmhaving a thickness of one nm to tens nm, the luminous efficiency ofyellow light increases to increase the intensity of yellow light, andwhen the light emitting layer 102 c is made of a single layer ormultilayer film having a thickness of tens nm to 10 μm, the absorptionefficiency of blue light increases to increase the intensity of yellowlight. The two cladding layers 102 a and 102 b on both sides of thelight emitting layer 102 c have a greater band gap than the lightemitting layer 102 c. That is, the semiconductor laminate 2 has adouble-hetero structure. Because of the double-hetero structure,electrons and holes generated by the blue light E1 emitted from thesemiconductor light emitting element 1 can be effectively confined inthe light emitting layer 102 c, so that the luminous efficiency of theyellow light E2 can increase to increase the emission luminance of theyellow light E2. Also, because of the double-hetero structure, theemission luminance of the yellow light E2 increases even if the lightemitting layer 102 c is made of a single layer film. If the claddinglayers for locating the light emitting layer 102 c are p-type and n-typecladding layers as in this preferred embodiment, the intensity of theyellow light E2 of the light emitting layer 102 c further increases.This results was obtained by the inventors experiment. It is analyzedthat the reason for this is that the absorption efficiency is increasedby the internal field. No element may be doped into the cladding layers102 a and 102 b. In the case of such undoping, the crystallinecharacteristics of the light emitting layer 102 c are improved, i.e.,the non-emission center of the light emitting layer 102 decreases, andthe intensity of the yellow light E2 in the light emitting layer 102 cincreases.

[0121] When the semiconductor laminate 2 having the double-heterostructure is used as in the device of FIG. 11, the area of thesemiconductor laminate 2 is preferably set to be ⅓ to ⅔ of the area ofthe sapphire substrate 104 on the top side in the figure. That is, asdescribed above, when the semiconductor laminate 2 has the double-heterostructure, the intensity of the yellow light E2 increases. However, ifthe double-hetero structure is used, the n-type cladding layer 102 aabsorbs the blue light E1, so that the intensity of the blue light E1decreases. Therefore, when the semiconductor laminate 2 is thedouble-hetero structure and when the area of the semiconductor laminate2 has the same as that on the top side in the figure, the intensity ofthe yellow light E2 is too strong, so that the tone of white light iscaused to approach yellow. Therefore, if the area of the semiconductorlaminate 2 is set to be ⅓ to ⅔ of the area of the sapphire substrate, itis possible to obtain white light having a good balance.

[0122] The thickness of the above described p-type cladding layer 102 bis preferably 300 nm or less, and more preferably 100 nm or less. Thereason for this is that the quantity of blue light E1 for exciting thelight emitting layer 102 c decreases when the p-type cladding layer 102b is too thick since the p-type cladding layer 102 b has the property ofabsorbing blue light E1. On the other hand, since the n-type claddinglayer 102 a has the property of transmitting yellow light E2, itsthickness may be increased if necessary.

[0123] As shown in FIG. 11, the semiconductor laminate 2 is bonded to apart of the top side of the sapphire substrate 104 of the semiconductorlight emitting element 1 in the figure. For example, this semiconductorlaminate 2 may be formed by sequentially forming the n-type claddinglayer 102 a, the light emitting layer 102 c and the p-type claddinglayer 102 b on the GaAs substrate, heat-treating the substrate at atemperature of 460° C. to 750° C. in an atmosphere of an inert gas,bonding the p-type cladding layer 102 b on the top side of the sapphiresubstrate 104 in the figure, and etching and removing the GaAssubstrate.

[0124] In the above described semiconductor light emitting element 1 andsemiconductor laminate 2, blue light E1 is emitted from the active layer104 of the semiconductor light emitting element 1, and a part of theblue light E1 is incident on the semiconductor laminate 2. The incidentblue light E1 excites the light emitting layer 102 c of thesemiconductor laminate 2, so that yellow light E2 is emitted from thelight emitting layer 102. Thus, the blue light E1 emitted from theactive layer 107 and the yellow light E2 emitted from the light emittinglayer 102 c are mixed to realize white light.

[0125] Referring to the chromaticity diagram of FIG. 12, this whitelight will be described below in detail. FIG. 12 is an xy chromaticitydiagram defined by International Commission on Illumination (CIE). Theemission wavelength of an InGaAlN active layer, such as the active layer107 a of the semiconductor light emitting element 1 of FIG. 11, can bein the range of from 380 nm to 500 nm as shown on the left side of FIG.12. The emission wavelength of an InGaAlP light emitting layer, such asthe light emitting layer 102 c of the semiconductor laminate 2, can bein the range of from 540 nm to 750 nm as shown on the right side of FIG.12. If for example, the color mixture of blue light having a wavelengthof 476 nm emitted from the InGaAlN active layer with yellow light havinga wavelength of 578 nm emitted from the InGaAlP light emitting layer isintended to be carried out, a straight line drawn between a white circleof 476 in the lower-left blue region and a white circle of 578 in theupper-right yellow region is considered. Then, it can be seen that thisstraight line passes through a white region. It can thus be seen fromFIG. 12 that white light can be realized by the color mixture of theblue light emitted from the semiconductor light emitting element 1 andthe yellow light E2 emitted from the semiconductor laminate 2.

[0126] Similarly, it can be seen from FIG. 12 that white light can berealized by the color mixture of bluish green light with red light whenthe emission wavelength of the InGaAlN active layer 107 a is set to be495 nm and the emission wavelength of the InGaAlP light emitting layer102 c is set to be 750 nm.

[0127] In the above described semiconductor of FIG. 11, it is possibleto decrease the variation in tone in each device. This is because unlikefluorescent material, the thickness, composition, and othercharacteristics and area of the semiconductor laminate 2 hardly vary ineach element. That is, by using a standardized mass production processgenerally used for the manufacturing of semiconductor elements, thesemiconductor laminate 2 can be manufactured with high repeatability sothat the thickness, composition and other characteristics hardly vary,and can be easily worked so as to have the same area. Then, when thethickness, composition, and other characteristics and area of thesemiconductor laminate 2 are uniform for each element, the ratio of theblue light E1 emitted from the semiconductor light emitting element 1 tothe yellow light E2 emitted from the semiconductor laminate 2 does notvary for each element, so that the tone does not vary for each element.

[0128] In the semiconductor light emitting device of FIG. 11, the tonecan also be adjusted by changing the area of the semiconductor laminate2. Because of this, when the luminous efficiency of the semiconductorlaminate 2 varies for some reason or other, for example, the tone can beadjusted. In a simple manner, the luminous efficiency of thesemiconductor laminate 2 decreases, the area of the semiconductorlaminate may be increased.

[0129] Also, it is necessary to change the tone of white light isintended, the tone can be easily changed by changing the area of thesemiconductor laminate 2 as described above. For example, when anelement for emitting white light having a tone close to blue is intendedto be manufactured as a displaying element, the area of thesemiconductor laminate 2 for emitting yellow light may be decreased.

[0130] Moreover, in the semiconductor light emitting device of FIG. 11,it is possible to further improve the emission luminance than that inconventional elements. That is, since the semiconductor laminate 2 isformed only on a part of the light emitting surface in the element ofFIG. 11, it is possible to utilize blue light which does not passthrough the semiconductor laminate 2 serving as a wavelength convertingregion, i.e., blue light having a high luminance directly emitted fromthe semiconductor light emitting element 1, so that it is possible toimprove the emission luminance.

Ninth Preferred Embodiment

[0131] As can be seen from FIG. 13, one of different points of the ninthpreferred embodiment from the eighth preferred embodiment is that alight emitting surface is arranged on the side of a p-type contact layer109.

[0132]FIG. 13 is a schematic sectional view of the ninth preferredembodiment of a semiconductor white light emitting device according tothe present invention. As in the case with the eighth preferredembodiment (FIG. 11), a semiconductor white light emitting devicecomprises a semiconductor light emitting element 1 for emitting bluelight E1 from an active layer 107 by current injection, and asemiconductor laminate 2 excited by the blue light E1 for emittingyellow light E2 from a light emitting layer 102. These light beams areemitted from the light emitting surface on the top side in the figure.

[0133] First, the structure of the semiconductor light emitting element1 is basically the same as that in the first preferred embodiment (FIG.1), so that the detailed description thereof is omitted.

[0134] The semiconductor laminate 2 will be described below. Thesemiconductor laminate 2 has a structure wherein a light emitting layer102 of an InAlP/InGaAlP multilayer film is located between a p-typeInGaAlP cladding layer 102 b and an n-type InGalP cladding layer 102 a.On the bottom side of the n-type cladding layer 102 a, a reflecting film120 for reflecting yellow light emitted from the light emitting layer102 is formed. This reflecting film may be made of a metal film of Al,Ag, Au or Cu or an alloy thereof, and have a thickness of 0.1 μm to 10μm. Thus, the yellow light E2 emitted from the light emitting layer 102downward in the figure can be reflected on the reflecting film 120 to beemitted from the light emitting surface. The semiconductor laminate 2thus manufactured is bonded to a part of the bottom face (second face)in the figure of the sapphire substrate 104 of the semiconductor lightemitting element 1.

[0135] Even if the light emitting surface is arranged on the side of thep-type contact layer 109 as in this preferred embodiment, the sameadvantages as those in the eighth preferred embodiment can be obtained.

Tenth Preferred Embodiment

[0136] As can be seen from FIG. 14, one of different points of the tenthpreferred embodiment from the ninth preferred embodiment is that asemiconductor laminate 2 is formed on the side of a light emittingsurface on the top side in the figure.

[0137]FIG. 14 is a schematic sectional view of the tenth preferredembodiment of a semiconductor white light emitting device according tothe present invention. As in the case with the ninth preferredembodiment (FIG. 13), a semiconductor white light emitting devicecomprises a semiconductor light emitting element 1 for emitting bluelight E1 from an active layer 107 by current injection, and asemiconductor laminate 2 excited by the blue light E1 for emittingyellow light E2 from a light emitting layer 102. As can be seen fromFIG. 14, the light emitted from this device is emitted from the lightemitting surface on the top side in the figure.

[0138] First, the semiconductor light emitting element 1 will bedescribed. One of different points of the semiconductor light emittingelement 1 from that in the ninth preferred embodiment (FIG. 13) is thata reflecting layer 120 for reflecting blue light E1 emitted from anactive layer 107 and yellow light E2 emitted from a light emitting layer102 is formed on the bottom side of a sapphire substrate 104. Thisreflecting film may be made of a metal film of Al, Ag, Au or Cu or analloy thereof, and have a thickness of 0.1 μm to 10 μm. Thus, the bluelight E1 emitted from the active layer 107 downward in the figure andthe yellow light E2 emitted from the light emitting layer 102 downwardin the figure can be reflected on the reflecting film 120 to be emittedfrom the light emitting surface on the top side in the figure. Otherprincipal structures are the same as those in the ninth preferredembodiment (FIG. 9).

[0139] The semiconductor laminate 2 will be described below. As in thecase with the ninth preferred embodiment, the semiconductor laminate 2has a structure wherein the light emitting layer 102 of an InAlP/InGaAlPmultilayer film is located between a p-type InGaAlP cladding layer 102 band an n-type InGaAlP cladding layer 102 a. This semiconductor laminate2 is bonded to the top of a p-side transparent electrode 110 a of thesemiconductor light emitting element 1. As in the case with the eighthpreferred embodiment, a heat treatment is carried out in an atmosphereof an inert gas during bonding. However, as a result of the inventors'experiment, the bonding temperature for the semiconductor laminate 2 maybe in the range of from 150° C. to 450° C. although the bondingtemperature in the eighth embodiment is in the range of from 460° C. to750° C. That is, as a result of the inventors' experiment, it was foundthat if the semiconductor laminate 2 was bonded to the top of thetransparent electrode 109, it is possible to bond it at a lowertemperature than the case where it was bonded to the sapphire substrate104, with the same bonding strength.

[0140] Even if the semiconductor laminate 2 is formed on the top of thetransparent electrode 110 a on the side of the light emitting surface asin the semiconductor light emitting device in this preferred embodiment,the same advantages as those in the ninth and eighth preferredembodiments can be obtained.

[0141] Since the semiconductor laminate 2 is bonded to the transparentelectrode 110 a in the semiconductor light emitting element in thispreferred embodiment, it is possible to utilize reflection on thetransparent electrode 110 a, so that it is possible to more effectivelyextract yellow light emitted from the light emitting layer 102.

Eleventh Preferred Embodiment

[0142] As can be seen from FIG. 15, one of different points of theeleventh preferred embodiment from the eighth preferred embodiment (FIG.11) is that an n-side electrode 111 is provided on the top of asubstrate 404 n using an n-type GaN substrate 404 n and that a low-passfilter 130 is provided in a semiconductor laminate 2.

[0143]FIG. 15 is a schematic sectional view of the eleventh preferredembodiment of a semiconductor white light emitting device according tothe present invention. Just like the eight preferred embodiment (FIG.11), a semiconductor white light emitting device comprises thesemiconductor light emitting element 1 for emitting blue light E1 froman active layer 107 by current injection, and a semiconductor laminate 2excited by the blue light E1 for emitting yellow light E2 from a lightemitting layer 102. The light emitted from this device is emitted fromthe light emitting surface on the top side in the figure.

[0144] First, the semiconductor light emitting element 1 will bedescribed. On the bottom face of an n-type GaN substrate 404 n in thefigure, there are sequentially formed an n-type AlGaN buffer layer 105n, an n-type GaN cladding layer 106, an active layer 107 having aGaN/InGaN multi-quantum well structure, a p-type AlGaN cladding layer108 and a p-type GaN contact layer 109. A current is injected into theactive layer 107 from an n-side electrode 111 of Ti/Al or the likeformed on the n-type GaN substrate 404 n and from a p-type electrode 110of Ni/Au or the like formed on the p-type contact layer 109. Asdescribed above, the buffer layer 105 n is made of an n-type AlGaN sincethe current is injected into the active layer 107 via the buffer layer105 n from then-side electrode 110 provided on the substrate 404 n inthe element of FIG. 15.

[0145] The semiconductor laminate 2 will be described below. Thesemiconductor laminate 2 has a structure wherein the light emittinglayer 102 of an InAlP/InGaAlP multilayer film is located between ap-type InGaAlP cladding layer 102 b and an n-type InGaAlP cladding layer102 a. In addition, in the device of FIG. 15, the semiconductor laminate2 is provided with the low-pass filter 130. As shown in FIG. 16, thelow-pass filter 130 has a high reflectance with respect to the yellowlight E2 emitted from the light emitting layer 102, and a lowreflectance with respect to the blue light E1 emitted from the activelayer 107. That is, the low-pass filter 130 has the property ofreflecting the yellow light E2 emitted from the light emitting layer 102and transmitting the blue light E1 emitted from the active layer 107. Asin the case with the eighth preferred embodiment (FIG. 11), thesemiconductor laminate 2 is bonded on the top side (the side of thesecond surface) of the substrate 404 n of the semiconductor lightemitting element 1 in the figure.

[0146] When the n-type GaN substrate 404 n is used as a substrate as inthe element in this preferred embodiment, the distortion due to thelattice unconformity between the substrate 404 n and the crystal growthlayers 105 n through 109 including the active layer 107 is decreased, sothat it is possible to realize a light emitting device having highreliability.

[0147] When the low-pass filter 130 is provided as in the device in thispreferred embodiment, it is possible to efficiently extract yellow lightemitted from the light emitting layer 107, so that it is possible tofurther enhance luminance.

[0148] While the n-type GaN substrate 404 n has been used as thesubstrate in the above described eleventh preferred embodiment, ann-type SiC substrate may be used as in the fourth preferred embodiment.When the n-type SiC substrate is used, it is possible to realize adevice which has good radiation characteristics and which does notdecrease luminance even at a high temperature of higher than 80° C.

Twelfth Preferred Embodiment

[0149] In the following twelfth and thirteenth preferred embodiments,there will be described other semiconductor white light emitting deviceswhich are relevant to the present invention and wherein the variation intone in each device is small.

[0150] As shown in FIG. 17, the twelfth preferred embodiment ischaracterized in that an ion implantation region 809 is provided in apart of an active layer 107.

[0151]FIG. 17 is a schematic sectional view showing the twelfthpreferred embodiment of a semiconductor white light emitting deviceaccording to the present invention. On the bottom face of a sapphiresubstrate 104 in the figure, there are sequentially formed a bufferlayer 105, an n-type GaN cladding layer 106, an active layer 107 havinga GaN/InGaN multi-quantum well structure, a p-type AlGaN cladding layer108 and a p-type GaN contact layer 109.

[0152] One of the features of this preferred embodiment is that the ionimplantation region 809 is provided to form an ion implanted region in apart of the active layer 107. Ions in the ion implantation region 809form the emission center in the active layer 107 to absorb blue light E1to emit yellow light E2. The device of FIG. 17 realizes white light bythe blue light E1 emitted from the active layer 107 and the yellow lightE2 emitted from the ion implantation region 809. These light beams areemitted from the light emitting surface on the top side in the figure.

[0153] A current is injected into the above described active layer 107from the n-side electrode 111 formed on the n-type cladding layer 106and from the p-side electrode 110 formed on the p-type contact layer109. The p-side electrode 110 and the n-side electrode 111 arepreferably made of Au/Ni and Ti/Al, respectively, which are materialhaving a high reflectance for reflecting blue light and yellow light.Because of this constitution, the blue light E1 emitted downward fromthe active layer 107 and the yellow light E2 emitted downward from theion implantation region 809 can be reflected on the p-side electrode 110and the n-side electrode 111 to be emitted from the light emittingsurface on the top side in the figure.

[0154] The semiconductor light emitting device of FIG. 17 can decreasethe variation in tone in each device. This is because the ionconcentration and implantation region in the ion implantation region 809hardly vary in each device. That is, since the ion implantation can becarried out with high repeatability by a standardized process generallyused in the manufacturing of semiconductor device, the ion concentrationand implantation region in the ion implantation region 809 is uniform ineach device. Thus, the ratio of the quantity of the blue light E1emitted from the active layer 107 to the quantity of the yellow light E2emitted from the ion implantation region 809 does not vary everyelement. Therefore, the tone does not vary device by device.

[0155] In the device of FIG. 17, even if the luminous efficiency of theactive layer 809 varies for some reason or other, the ratio of thequantity of the blue light E1 to the quantity of the yellow light E2 isthe same, so that the tone does not vary. For example, even if theluminous efficiency of the active layer 107 decreases for some reason orother, both of the blue light E1 and the yellow light E2 are weaken atthe same rate, and the ratio of the quantity of the blue light E1 to thequantity of the yellow light E2 is the same, so that the tone does notvary. Thus, the variation in tone in each device is very small in thedevice of FIG. 17.

[0156] In the semiconductor light emitting device of FIG. 17, it ispossible to easily adjust the tone by changing the area of the ionimplantation region 809. By doing so, it is possible to easily vary thetone of white light if necessary. For example, when a device foremitting white light having a tone close to blue is intended to bemanufactured as a displaying device, the area of the ion implantationregion 809 may be decreased.

[0157] Moreover, in the semiconductor light emitting device of FIG. 17,the emission luminance can be made higher than that in conventionalelements. That is, light emitted directly from the semiconductor lightemitting element 1 can be utilized to increase the emission luminance.

Thirteenth Preferred Embodiment

[0158] As shown in FIG. 18, the thirteenth preferred embodiment ischaracterized in that fluorescent material 903 for emitting yellow lightE2 are formed in part of a reflector 902.

[0159]FIG. 18 is a schematic sectional view showing the thirteenthpreferred embodiment of a semiconductor white light emitting deviceaccording to the present invention. The semiconductor light emittingdevice comprises a semiconductor light emitting element 1 for emittingblue light E1, a reflector 902 for reflecting the blue light E1 emittedfrom the semiconductor light emitting element 1, and a fluorescentmaterial 903 applied on several parts of the reflecting surface of thereflector 902 for converting the wavelength of the blue light E1 to emityellow light E2. The semiconductor light emitting element 1 and thereflector 902 are integrally formed of a mold resin 904. Thesemiconductor light emitting element in the ninth preferred embodiment(FIG. 13) may be used as the semiconductor light emitting element 1 inthis embodiment. The fluorescent material 903 may be formed of, e.g.,YAG:Ce. The fluorescent material 903 is thinly applied on the severalpart of the reflecting surface of the reflector 902 so as to have asmall thickness.

[0160] The device of FIG. 18 realizes white light by the blue light E1reflected on the reflector 902 and the yellow light E2 emitted on thefluorescent material 903.

[0161] The semiconductor light emitting device of FIG. 18 can decreasethe variation in tone in each device. The reason for this is as follows.

[0162] First, the area of fluorescent material regions, on which thefluorescent material 903 is applied, hardly varies in each device. Thatis, since the surface of the reflector 902 is even, it is possible toeasily adjust the area thereof, so that the area of the fluorescentmaterial regions hardly varies in each device.

[0163] Secondly, when the volume of a fluorescent material region varieswhile maintaining the area thereof on which the fluorescent material isapplied, the variation in tone in each device is small. That is, in theapplied fluorescent material 903 in the fluorescent material region, aportion near the semiconductor light emitting element 900, i.e., aportion near the surface of the fluorescent material region, has a highconversion efficiency for converting the blue light E1 into the yellowlight E2, and even if the thickness of the fluorescent material regionvaries, the quantity of the fluorescent material 903 arranged near thesurface of the fluorescent material region and having a high conversionefficiency does not vary, and it is only the quantity of the fluorescentmaterial 903 having a low conversion efficiency that varies. Thus, evenif the thickness of the fluorescent material region varies, the quantityof the fluorescent material 903 having a high conversion efficiency andhaving a great influence on the intensity of the yellow light E2 hardlyvaries. Therefore, even if the thickness of the fluorescent materialregion varies, this variation has a little influence on the intensity ofthe yellow light E2, so that the variation in tone in each device issmall.

[0164] Thus, the semiconductor light emitting device of FIG. 18 candecrease the variation in tone in each device.

[0165] The semiconductor light emitting device of FIG. 18 can easilyadjust the tone by changing the area of the fluorescent material regionson which the fluorescent materials 903 is applied. Thus, for example,even if the conversion efficiency of the fluorescent material 903varies, it is possible to adjust the tone easily. For example, when theconversion efficiency of the fluorescent material 903 decreases, thetone may be adjusted by increasing the area of the fluorescent materialregions.

[0166] In addition, the semiconductor light emitting device of FIG. 18can adjust the tone by changing the area of the fluorescent materialregion on which the fluorescent material 903 is applied. Thus, it ispossible to easily change the tone of white light if necessary. Forexample, when a device for emitting white light having a tone close toblue is intended to be manufactured, the area of the fluorescentmaterial regions may be decreased.

[0167] Since the fluorescent material is applied on the reflector in thesemiconductor light emitting device of FIG. 18, it is possible to easilyadjust the angle of visibility.

[0168] Moreover, the semiconductor light emitting device of FIG. 18 canfurther improve the emission luminance than conventional devices. Thatis, in the device of FIG. 18, it is possible to utilize light emitteddirectly from the semiconductor light emitting device, and it ispossible to increase the conversion efficiency of the fluorescentmaterial 903 by widely and thinly applying the fluorescent material,thereby improving the emission luminance.

[0169] While the present invention has been disclosed in terms of thepreferred embodiment in order to facilitate better understandingthereof, it should be appreciated that the invention can be embodied invarious ways without departing from the principle of the invention.Therefore, the invention should be understood to include all possibleembodiments and modification to the shown embodiments which can beembodied without departing from the principle of the invention as setforth in the appended claims.

What is claimed is:
 1. A semiconductor light emitting device comprising:a semiconductor light emitting element which has an active layer foremitting primary light having a first wavelength by current injection;and at least one semiconductor laminate which is bonded to saidsemiconductor light emitting element and which has a light emittinglayer, excited by said primary light, for emitting secondary lighthaving a second wavelength different from said first wavelength, whereinsaid primary light and said secondary light are mixed to be outputted.2. A semiconductor light emitting device as set forth in claim 1,wherein said active layer is a In_(p)Ga_(q)Al_(1−p−q)N(O≦p≦1, 0≦q≦1,0≦p+q≦1) active layer, and said light emitting layer is anIn_(b)Ga_(c)Al_(1−b−c)P (0≦b≦1, 0≦c≦1, 0≦b+c≦1) light emitting layer. 3.A semiconductor light emitting device as set forth in claim 2, whereinsaid active layer is an active layer for emitting blue light, and saidlight emitting layer is a light emitting layer, excited by the bluelight emitted from said active layer, for emitting yellow light.
 4. Asemiconductor light emitting device as set forth in claim 1, whereinsaid semiconductor laminate has a first light emitting layer excited bysaid primary light for emitting said secondary light, and a second lightemitting layer, excited by said primary light and said secondary light,for emitting tertiary light having a third wavelength.
 5. Asemiconductor light emitting device as set forth in claim 4, whereinsaid active layer is an In_(p)Ga_(q)Al_(1−p−q)N(0≦p≦1, 0≦q≦1, 0≦p+q≦1)active layer for emitting blue light, said first light emitting layer isan In_(b)Ga_(c)Al_(1−b−c)P (0≦b≦1, 0≦c≦1, 0≦b+c≦1) light emitting layer,excited by said blue light emitted from said active layer, for emittinggreen light, and said second light emitting layer is anIn_(x)Ga_(y)Al_(1−x−y)P (0≦x≦1, 0≦y≦1, 0≦x+y≦1) light emitting layer,excited by said blue light and said green light, for emitting red light.6. A semiconductor light emitting device as set forth in claim 2,wherein said light emitting layer is a light emitting layer of anInAlP/InGaAlP multilayer film.
 7. A semiconductor light emitting deviceas set forth in claim 6, wherein said semiconductor laminate has astructure wherein said light emitting layer is located between anIn_(d)Ga_(e)Al_(1−d−e)P (0≦d≦1, 0≦e≦1, 0≦d+e≦1) cladding layer and aGaAs substrate, and a surface of said semiconductor laminate on the sideof said In_(d)Ga_(s)Al_(1−d−e)P cladding layer is bonded to a surface ofsaid semiconductor light emitting element opposite to a light emittingsurface.
 8. A semiconductor light emitting device as set forth in claim6, wherein said semiconductor laminate has a structure wherein saidlight emitting layer is located between an In_(d)Ga_(e)Al_(1−d−e)P(0≦d≦1, 0≦e≦1, 0≦d+e≦1) cladding layer and a protection layer, and asurface of said semiconductor laminate on the side of saidIn_(d)Ga_(e)Al_(1−d−e)P cladding layer is bonded to said semiconductorlight emitting element.
 9. A semiconductor light emitting device as setforth in claim 6, wherein said semiconductor laminate has a structurewherein said light emitting layer is located between anIn_(d)Ga_(e)Al_(1−d−e)P(0≦d≦1, 0≦e≦1, 0≦d+e≦1) cladding layer and asubstrate capable of transmitting said secondary light emitted from saidlight emitting layer, and a surface of said semiconductor laminate onthe side of said In_(d)Ga_(e)Al_(1−d−e)P cladding layer is bonded tosaid semiconductor light emitting element.
 10. A semiconductor lightemitting device as set forth in claim 2, wherein said active layer is anactive layer having a GaN/InGaN multi-quantum well structure.
 11. Asemiconductor light emitting device as set forth in claim 2, whereinsaid semiconductor light emitting element comprises: a substrate havingfirst and second surfaces; a buffer layer formed on said first surfaceof said substrate; a first conductive typeIn_(r)Ga_(s)Al_(1−r−s)N(0≦r≦1, 0≦s≦1, 0≦r+s≦1) cladding layer formed onsaid buffer layer; said active layer formed on said first conductivetype In_(r)Ga_(s)Al_(1−r−s)N cladding layer; and a second conductivetype In_(t)GaAl_(1−t−u)N(0≦t≦1, 0≦u≦1, 0≦t+u≦1) cladding layer formed onsaid active layer.
 12. A semiconductor light emitting device as setforth in claim 2, wherein said semiconductor light emitting elementcomprises: a sapphire substrate having first and second surfaces; abuffer layer formed on said first surface of said sapphire substrate; ann-type In_(r)Ga_(s)Al_(1−r−s)N(0≦r≦1, 0≦s≦1, 0≦r+s≦1) cladding layerformed on said buffer layer; said active layer formed on said n-typeIn_(r)Ga_(s) Al_(1−r−s)N cladding layer; a p-typeIn_(t)Ga_(u)Al_(1−t−u)N(0≦t≦1, 0≦u≦1, 0≦t+u≦1) cladding layer formed onsaid active layer; a p-type In_(v)Ga_(w)Al_(1−v−w)N(0≦v≦1, 0≦w≦1,0≦v+w≦1) contact layer formed on said p-type In_(t)Ga_(u)Al_(1−t−u)Ncladding layer; a p-side electrode formed on said p-typeIn_(V)Ga_(W)Al_(1−V−W) N contact layer; and an n-side electrode formedon said n-type In_(r)Ga_(s)Al_(1−r−s)N(0≦r≦1, 0≦s≦1, 0≦r+s≦1) claddinglayer exposed by etching.
 13. A semiconductor light emitting device asset forth in claim 2, wherein said semiconductor light emitting elementcomprises: an n-type semiconductor substrate having first and secondsurfaces; a buffer layer formed on said first surface of said substrate;an n-type In_(r)Ga_(s)Al_(1−r−s)N(0≦r≦1, 0≦s≦1, 0≦r+s≦1) cladding layerformed on said buffer layer; said active layer formed on said n-typeIn_(r)Ga_(s)Al_(1−r−s)N cladding layer; a p-typeIn_(t)Ga_(u)Al_(1−t−u)N(0≦t≦1, 0≦u≦1, 0≦t+u≦1) cladding layer formed onsaid active layer; a p-type In_(v)Ga_(w)Al_(1−v−w)N(0≦v≦1, 0≦w≦1,0≦v+w≦1) contact layer formed on said p-type In_(t)Ga_(u)Al_(1−t−u)Ncladding layer; and a p-side transparent electrode formed on said p-typeIn_(V) Ga_(W) Al_(1−V−W)N contact layer, light being emitted from theside of said p-type In_(V)Ga_(W)Al_(1−V−W)N contact layer, and whereinsaid semiconductor laminate comprises: an n-type GaAs substrate havingfirst and second surfaces; said light emitting layer of an n-typeInAlP/InGaAlP multilayer film formed on said first surface of saidn-type GaAs substrate; an n-type In_(d)Ga_(e)Al_(1−e−d)P(0≦d≦1, 0≦e≦1,0≦d +e≦1) cladding layer formed on said light emitting layer; and ann-side electrode formed on said second surface of said n-type GaAssubstrate, said n-type In_(d)Ga_(e)Al_(1−d−e)P cladding layer of saidsemiconductor laminate being bonded to said second surface of saidn-type semiconductor substrate of said semiconductor light emittingelement.
 14. A semiconductor light emitting device as set forth in claim13, wherein said n-type semiconductor substrate is made of a materialselected from the group consisting of n-type GaN, n-type SiC and n-typeSi.
 15. A semiconductor light emitting device as set forth in claim 2,wherein said semiconductor light emitting element comprises: a substratehaving first and second surfaces; a buffer layer formed on said firstsurface of said substrate; a first conductive typeIn_(r)Ga_(s)Al_(1−r−s)N(0≦r≦1, 0≦s≦1, 0≦r+s≦1) cladding layer formed onsaid buffer layer; said active layer formed on said first conductivetype In_(r) Ga_(s)Al_(1−r−s)N cladding layer; a second conductive typeIn_(t)Ga_(u)Al_(1−t−u)N(0≦t≦1, 0≦u≦1, 0≦t+u≦1) cladding layer formed onsaid active layer; and a second conductive typeIn_(v)Ga_(w)Al_(1−v−w)N(0v≦1, 0w≦1, 0≦v+w≦1) contact layer formed onsaid In_(t)Ga_(u)Al_(1−t−u)N cladding layer; wherein light is emittedfrom the side of said second conductive type In_(v)Ga_(w)Al_(1−v−w)Ncontact layer, said semiconductor laminate being bonded on said secondsurface of said substrate.
 16. A semiconductor light emitting device asset forth in claim 2, wherein said semiconductor light emitting elementcomprises: a substrate having first and second surfaces; a buffer layerformed on said first surface of said substrate; a first conductive typeIn_(r)Ga_(s)Al_(1−r−s)N(0≦r≦1, 0≦s 1, 0≦r+s≦1) cladding layer formed onsaid buffer layer; said active layer formed on said first conductivetype In_(r) Ga_(s)Al_(1−r−s)N cladding layer; a second conductive typeIn_(t)Ga_(u)Al_(1−t−u)N(0≦t≦1, 0≦u≦1, 0≦t+u≦1) cladding layer formed onsaid active layer; and a second conductive typeIn_(t)Ga_(w)Al_(1−v−w)N(0≦v≦1, 0≦w≦1, 0≦v+w≦1) contact layer formed onsaid In_(t)Ga_(u) Al_(1−t−u)N cladding layer; wherein light is emittedfrom said second surface of said substrate, said semiconductor laminatebeing bonded on said second surface of said substrate.
 17. Asemiconductor light emitting device comprising: a GaAs substrate; anIn_(b)Ga_(c)Al_(1−b−c)P(0≦b≦1, 0≦c≦1, 0≦b+c≦1) light emitting layerwhich is formed on said GaAs substrate and which is excited by primarylight having a first wavelength for emitting secondary light having asecond wavelength; a buffer layer formed on said In_(b)Ga_(c)Al_(1−b−c)Plight emitting layer; and a Zn_(j)Cd_(1−j)Se (0≦j≦1) active layer whichis formed on said buffer layer and which emits said primary light havingthe first wavelength by current injection; wherein said primary lightand said secondary light are mixed to be outputted.
 18. A method formanufacturing a semiconductor light emitting device, said methodcomprising: a semiconductor light emitting element forming on a firstsubstrate step including a step of forming a semiconductor layers, whichhas an active layer for emitting primary light having a first wavelengthby current injection; a semiconductor laminate forming step including astep of forming on a second substrate a semiconductor layer, whichincludes a light emitting layer excited by said primary light foremitting secondary light having a second wavelength different from saidfirst wavelength; and a bonding step including a step of integrallybonding said semiconductor light emitting element to said semiconductorlaminate.
 19. A method for manufacturing a semiconductor light emittingdevice as set forth in claim 18, wherein said active layer is anIn_(p)Ga_(q)Al_(1−p−q)N(0≦p≦1, 0≦q≦1, 0≦p+q≦1) active layer, and saidlight emitting layer is an In_(b)Ga_(c)Al_(1−b−c)P(0≦b≦1, 0 ≦c≦1,0≦b+c≦1) light emitting layer.
 20. A method for manufacturing asemiconductor light emitting device as set forth in claim 19, whereinsaid semiconductor light emitting element forming step comprises thesteps of: forming a buffer layer on said first substrate; forming afirst conductive type In_(r)Ga_(s)Al_(1−r−s)N(0≦r≦1, 0≦s≦1, 0≦r+s≦1)cladding layer on said buffer layer; forming said active layer on saidfirst conductive type In_(r)Ga_(s Al) _(1−r−s)N(0≦r≦1, 0s≦1, 0≦r+s≦1)cladding layer; and forming a second conductive typeIn_(t)Ga_(u)Al_(1−t−u)N(0≦t≦1, 0≦u≦1, 0≦t+u≦1) cladding layer on saidactive layer, said semiconductor laminate forming step comprising thesteps of forming said light emitting layer on said second substrate, andforming an In_(d)Ga_(e)Al_(1−d−e)P(0≦d≦1, 0≦e≦1, 0≦d+e≦1) cladding layeron said light emitting layer, said bonding step comprising a step ofintegrally bonding said semiconductor light emitting element to saidIn_(d)Ga_(e)Al_(1−d−e)p cladding layer of said semiconductor laminate.21. A method for manufacturing a semiconductor light emitting device asset forth in claim 20, wherein said light emitting layer is a lightemitting layer of an InAlP/InGaAlP multilayer film and which furthercomprises, after said bonding step, a second substrate removing stepincluding a step of removing said second substrate to expose said lightemitting layer, and a protection layer forming step including a step offorming a protection layer on said light emitting layer exposed by saidsecond substrate removing step.
 22. A method for manufacturing asemiconductor light emitting device as set forth in claim 20, whereinsaid light emitting layer is a light emitting layer of an InAlP/InGaAlPmultilayer film, and which further comprises, after said bonding step, asecond substrate removing step including a step of removing said secondsubstrate to expose said light emitting layer, and a third substratebonding step including a step of a bonding third substrate, which hasthe property of transmitting said primary light emitted from said activelayer and said secondary light emitted from said light emitting layer,to said light emitting layer exposed in said second substrate removingstep.
 23. A method for manufacturing a semiconductor light emittingdevice, said method comprising the steps of: forming on a GaAs substratean In_(b)Ga_(c)Al_(1−b−c)P(0≦b≦1, 0≦c≦1, 0≦b+c≦1) light emitting layer,which is excited by blue light for emitting yellow light; forming abuffer layer on said In_(b)Ga_(c)Al_(1−b−c)P light emitting layer; andforming on said buffer layer a Zn_(j)Cd_(1−j)Se (0≦j≦1) active layer,which emits said blue light by current injection.
 24. A semiconductorlight emitting device as set forth in claim 2, wherein saidsemiconductor laminate has a structure wherein said light emitting layeris located between an In_(d)Ga_(e)Al_(1−d−e)P(0≦d≦1, 0≦e≦1, 0≦d+e≦1)cladding layer and an In_(f)Ga_(h)Al_(1−f−h)P(0≦f≦1, 0≦h≦1, 0≦f+h≦1)cladding layer and said semiconductor laminate on the side of saidIn_(f)Ga_(h)Al_(1−f−h)P cladding layer is bonded to a portion of saidsemiconductor light emitting element.
 25. A semiconductor light emittingdevice as set forth in claim 2, wherein said semiconductor lightemitting element comprises: an n-type semiconductor substrate havingfirst and second surfaces; a buffer layer formed on said first surfaceof said substrate; an n-type In_(r)Ga_(s)Al_(1−r−s)N(0≦r≦1, 0≦s≦1,0≦r+s≦1) cladding layer formed on said buffer layer; said active layerformed on said n-type In_(r)Ga_(s)Al_(1−r−s)N cladding layer; a p-typeIn_(t)Ga_(u)Al_(1−t−u)N(0≦t≦1, 0≦u≦1, 0≦t+u1) cladding layer formed onsaid active layer; a p-type In_(v)Ga_(w)Al_(1−v−w)N(0≦v≦1, 0≦w≦1,0≦v+w≦1) contact layer formed on said p-type In_(t)Ga_(u)Al_(1−t−u)Ncladding layer; a p-side transparent electrode formed on said p-typeIn_(v)Ga_(w)Al_(1−v−w)N contact layer; and an n-side electrode formed onsaid second surface of said n-type semiconductor substrate.
 26. Asemiconductor light emitting device as set forth in claim 2, whereinsaid semiconductor light emitting element comprises: a substrate havingfirst and second surface; a buffer layer formed on said first surface ofsaid n-type semiconductor substrate; a first conductive typeIn_(r)Ga_(s)Al_(1−r−s)N(0≦r≦1, 0≦s≦1, 0≦r+s≦1) cladding layer formed onsaid buffer layer; said active layer formed on said first conductivetype In_(r) Ga_(s)Al_(1−r−s)N cladding layer; a second conductive typeIn_(t)Ga_(u)Al_(1−t−u)N(0≦t≦1, 0≦u≦1, 0≦t+u≦1) cladding layer formed onsaid active layer; and a second conductive typeIn_(v)Ga_(w)Al_(1−v−w)N(0≦v≦1, 0≦w≦1, 0≦v+w≦1) contact layer formed onsaid In_(t)Ga_(u)Al_(1−t−u)N cladding layer; wherein light is emittedfrom the side of said second conductive type In_(v)Ga_(w)Al_(1−v−w)Ncontact layer, and wherein said semiconductor laminate is bonded on saidsecond conductive type In_(v)Ga_(w)Al_(1−v−w)N contact layer.
 27. Amethod for manufacturing a semiconductor light emitting device as setforth in claim 20, wherein said semiconductor laminate forming stepcomprises the steps of: forming a In_(d)Ga_(e)Al_(1−d−e)P(0≦d≦1, 0≦e≦1,0≦d+e≦1) cladding layer on a GaAs substrate serving as said secondsubstrate; forming said light emitting layer on saidIn_(d)Ga_(e)Al_(1−d−e)P cladding layer; and forming aIn_(f)Ga_(h)Al_(1−f−h)P(0≦f≦1, 0≦h≦1, 0≦f+h ≦1) cladding layer on saidlight emitting layer, said method further comprising, after said bondingstep, a GaAs substrate removing step of removing said GaAs substrate toexpose said In_(d)Ga_(e)Al_(1−d−e)P cladding layer.
 28. A semiconductorlight emitting device comprising: a substrate; a buffer layer formed onsaid substrate; a first conductive type In_(r)Ga_(s)Al_(1−r−r)N(0≦r≦1,0≦s≦1, 0≦r+s≦1) cladding layer formed on said buffer layer, anIn_(p)Ga_(q)Al_(1−p−q)N(0≦p≦1, 0≦q≦1, 0≦p+q≦1) active layer formed onsaid first conductive type In_(r)Ga_(s)Al_(1−r−s)N cladding layer andprovided with an ion implantation region into which ions selected fromthe group consisting of fluorine, oxygen, nitrogen, carbon and sulfurhave been injected, regions other than said ion implantation regionemitting primary light having a first wavelength, and said ionimplantation region emitting secondary light having a second wavelengthdifferent from said first wavelength; and a second conductive typeIn_(t)Ga_(u)Al_(1−t−u)N(0≦t≦1, 0≦u≦1, 0≦t+u≦1) cladding layer formed onsaid active layer.
 29. A semiconductor light emitting device comprising:a semiconductor light emitting element which has an active layer foremitting primary light having a first wavelength by current injection;reflector for reflecting said primary light emitted from saidsemiconductor light emitting element; and fluorescent material which isapplied on part of said reflector and which is excited by said primarylight for emitting secondary light having a second wavelength differentform said first wavelength.